This invention relates generally to anionic surfactants and, more particularly, to substantially unsaturated fatty alcohol polyglycol ethers which, through the presence of branches in the hydrocarbon chain, are distinguished from linear homologs by significantly improved properties, to a process for their production and to their use for the production of surface-active compositions.
Fatty alcohol polyglycol ethers, which are essentially obtained by ethoxylation and/or propoxylation of the corresponding tallow-based alkenols, are important raw materials for the production of both cosmetic preparations and laundry detergents, dishwashing detergents and cleaning products. The favorable properties of these substances are linked to the presence of the double bond in the molecule which also presents problems because the unsaturated fatty alcohol polyglycol ethers readily fall victim to autoxidation which is associated with discoloration and unwanted chemical changes (for example formation of peroxides and hydroperoxides).
Accordingly, it is clear that there is a need on the market for unsaturated fatty alcohol polyglycol ethers with improved oxidation stability or suitable substitutes which possess at least equivalent performance properties. However, more or less pure isostearyl alcohol polyglycol ethers have hitherto been the only alternatives to unsaturated fatty alcohol polyglycol ethers. To produce these more or less pure isostearyl alcohol polyglyol ethers, however, oleic acid first has to be dimerized, the fraction of monomeric branched fatty acids separated off, hydrogenated and subjected to fractional crystallization, the liquid fraction accumulating, which is rich in isostearic acid, has to be removed and esterified with methanol and the esters obtained subsequently hydrogenated to form the alcohols which, finally, are converted into the polyglycol ethers.
The process described above is technically complicated by the two hydrogenation steps and, in the isostearyl alcohol polyglycol ethers, provides substitutes which can only replace the unsaturated fatty alcohol polyglycol ethers to a limited extent. Accordingly, the problem addressed by the present invention was to provide unsaturated unsaturated fatty alcohol polyglycol ethers which would be distinguished by improved performance properties and preferably by higher oxidation stability.